The invention relates to an image sensor device of the frame transfer type comprising a semiconductor substrate having a first region of a first conductivity type, a second region of a second conductivity type opposite to the first conductivity type arranged above the first region of the substrate, parallel charge transfer channels of the first conductivity type arranged in the second region in a direction of charge transfer and an arrangement of charge transfer electrodes perpendicular to the direction of charge transfer provided at the surface of the second region and electrically insulated therefrom in such a manner that they permit, when they are brought to suitable potentials, the transfer of charged of a first sign stored in elementary cells in response to incident light in the direction of charge transfer along the said parallel channels.
Such a device is known from European Pat. No. 143,496 filed by the Applicant.
In this prior art document, the channel regions are photosensitive and consequently only a part of the surface of the device is utilized, which limits the effectiveness.
Otherwise, it has been proposed for image sensor devices of the interline type to provide a photosensitive layer on the whole surface of the crystal and to connect this photosensitive layer electrically pointwise through electrodes to charge accumulation zones. An example of such a sensor is disclosed in European Pat. Application No. 139 366.
The charge transfer is effected, as is usual with this type of image sensor, due to a transfer channel distinct from the charge accumulation zone.
When a photosensitive layer is provided on the whole surface of the crystal, the advantage is obtained that the effectiveness of the device is increased because no geometric factor will reduce the dimensions of the sensitive surface.
However, the structure described is absolutely specific for an image sensor of the interline type (I.L.). In fact, in such sensors, since the charge accumulation zones and the charge transfer channels are mutually separated, the interconnections are formed due to multi-layer structures usual in the semiconductor industry.
The invention proposes for an image sensor device of the frame transfer type to provide a photosensitive layer on the surface of the crystal so that its effectiveness is increased.
The structures known hitherto for the sensors of the interline type (I.L.) are, as mentioned above, specific for such sensors. Their use in frame transfer devices would lead to utilizing a substantial part of the surface available for the interposition especially of electrodes connecting the photosensitive layer and charge transfer regions to each other.